The present invention relates to circuit cards, and more particularly, to a circuit card mounting system for housing circuit cards, and circular cards in particular.
A common way to mount cylindrical circuit cards in electronic housings is by using screws and standoffs. This system of mounting circuit cards requires areas on the circuit cards to be kept clear of components and circuitry, which reduces the usable area of the board. Multiple stacks of circuit cards using standoffs require close tolerance of screw holes, spacers, circuit card, and heat sink thicknesses, otherwise the ending tolerance stack up prevents a proper fit and alignment within the housing. The use of screws and standoffs also present added cost in fabrication because drilling and tapping operations are necessary. The elimination of torquing and alignment is virtually eliminated by the present invention.
If thermal requirements indicate that a thermal path to the housing is needed, sometimes elaborate (if not crude) devices are designed to accomplish a marginal amount of thermal heat transfer. The use of lightweight "touch" type connectors (woe strips, fuzz buttons, etc.) are difficult to use in standoff-type designs due to their inherent inability to provide for variable positioning. Distortion of circuit cards by use of screw fasteners may cause gaps between the contacts creating board malfunctions.
The present invention provides for an improved circuit card mounting system that may be used in a system such as is described in U.S. Pat. No. 5,251,099 entitled "High Density Electronics Package Having Stacked Circuit Boards", assigned to the assignee of the present invention, the contents of which are incorporated herein by reference. This patent discloses a high-density electronics package that houses a plurality of circuit cards, heat sinks and circuit interconnections in a single housing. The electronics package uses conical shaped interfaces for locating and locking components, which greatly enhances the serviceability, thermal management and strength of the electronics package. Assembly is accomplished by using a selected conical angle on a first heat sink that mates with a matching conical surface on the housing. A second heat sink has a conical angle (located in the opposite direction of the conical angle of the first heat sink) that mates with an identical angle on an expandable wedge ring used for positioning purposes. A small wedge shaped block is used to spread the second conical shaped ring and induce a compression load on all internal assemblies. This mounting feature provides automatic heat sink to heat sink axial alignment regardless of tolerances, therefore simplifying assembly and providing intimate contact between the heat sinks and the housing, and thus creating a thermal path from the circuit cards to the housing.
It is therefore an objective of the present invention to provide a circuit card mounting system for housing circuit cards.